Magnetic recording media have recently been developed to be used for higher density recording, and attention has shifted from magnetic particles of iron oxide to magnetic metal particles during the development of magnetic particles. As a magnetic recording medium using ferromagnetic metal particles, compact cassette tapes for audio recording has been realized and are now commercially available and widely used (metal cassette tape for metal position use).
Ferromagnetic metal particles enables one to select coercive force from a wide range and have greater magnetic moment than the conventional magnetic particles. Therefore, they can be widely used for various purposes and it seems that ferromagnetic metal particles can be commercially employed in various fields for higher density recording.
However, in preparing magnetic recording media, ferromagnetic metal particles exhibit certain problems due to the large magnetic moment, which is a characteristic feature thereof. That is, since the surface of ferromagntic metal particles is highly active and a large magnetic moment, the ferromagnetic metal particles have poor dispersibility in the binder, and therefore prolonged dispersion treatment has been found necessary, which is industrially disadvantageous. Furthermore, after the dispersion treatment is terminated, the resulting dispersion (a magnetic coating composition) coagulates after it is allowed to stand for a period of time.